865665819 has 16 divisors (see below), whose sum is σ = 1286526240. Its totient is φ = 575284320.

The previous prime is 865665817. The next prime is 865665833. The reversal of 865665819 is 918566568.

It is a happy number.

865665819 is a `hidden beast` number, since 8 + 6 + 56 + 6 + 581 + 9 = 666.

It is not a de Polignac number, because 865665819 - 2¹ = 865665817 is a prime.

It is a super-2 number, since 2×865665819² = 1498754620369881522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (865665811) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 42012 + ... + 59129.

It is an arithmetic number, because the mean of its divisors is an integer number (80407890).

Almost surely, 2^865665819 is an apocalyptic number.

865665819 is a deficient number, since it is larger than the sum of its proper divisors (420860421).

865665819 is a wasteful number, since it uses less digits than its factorization.

865665819 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 101467 (or 101461 counting only the distinct ones).

The product of its digits is 3110400, while the sum is 54.

The square root of 865665819 is about 29422.1994249240. The cubic root of 865665819 is about 953.0523499784.

The spelling of 865665819 in words is "eight hundred sixty-five million, six hundred sixty-five thousand, eight hundred nineteen".